The present invention involves an apparatus and process for recycling sewage sludge. In particular, the invention involves the blending and reduction of spent water-softener lime and sewage sludge to produce sludge ash which is reduced by approximately 90 percent and which can be either disposed in an approved landfill or can be incorporated as a binding agent or mineral filler in asphalt concrete, Portland cement concrete and gravel.
Recycling of waste products is a problem which has received considerable attention in an effort to protect the environment. Sewage sludge is a waste product which is typically treated and then either spread on land or is disposed in an approved landfill. Sewage sludge typically has high levels of heavy metals and pathogens. Consequently, where land spreading is practiced, the land can become unacceptably contaminated. Where sewage sludge is disposed of in approved landfills, transportation costs and dumping fees are incurred and the presence of heavy metals and pathogens in the waste product requires an accounting of each load by the landfill operator prior to dumping. Sewage sludge holds large quantities of water which increases the weight and volume of the sludge as well as the cost to dispose of it since dumping fees are typically charged based upon weight. Accordingly, it would be desirous to provide apparatus and a process by which sewage sludge is recycled in a way which reduces the water content of the waste, which removes pathogens from it and which creates a by-product that either can be incorporated into construction materials such as concrete and cement or land spread with less chance of soil contamination.
The present invention satisfies these needs by providing an alternative treatment for sewage sludge by blending it with spent water softener lime. Spent lime, after its use by water softening plants, is presently either being land spread or landfilled itself. Combining spent lime with sewage sludge and subjecting it to the steps of the present invention kills the pathogens in the sewage sludge, reduces the sludge ash by approximately 90 percent and renders a by-product which can be utilized as an aggregate substitute in the production of asphalt concrete, Portland Cement concrete or as a backfilling material for ditches or trenches. The by-product can also be used as a base stabilizer for wet soil during construction. Moreover, the recycled by-product can itself be land spread or deposited in an approved landfill at much less cost and with less danger to the environment because it weighs less and it has less potential for soil contamination.
It is an object of this invention to reduce the possibility of disease bearing air-borne bacteria and reduce the possibility of water contamination associated with sewage sludge.
It is a further object of the invention to reduce heavy metal contamination of the earth caused by disposal of sewage sludge.
Another object of the invention is to reduce unpleasant odors associated with land spreading and land-filling of sewage sludge.
A further object of the invention is reducing the cost including landfill tipping fees of sewage waste disposal.
It is an object of the invention to reduce the burden of record keeping due to elimination of pathogens from sewage waste.
It is an object of the invention to treat sewage sludge so as to provide a resultant material that can be used as an element of construction materials such as a mineral filler, binding agent, an aggregate substitute or aggregate equivalent.
Another object is to provide a valuable use for spent water softener lime which would otherwise need to be disposed, such as in a landfill or land spreading.
A further object of the invention is to provide a process by which spent water softener lime is recycled.
Another object is to treat sewage sludge so as to provide a binding agent for the concrete/cement block industry, asphalt industry and the construction industry.
Moreover, it is an object of the invention to provide a process by which for every ten tons of waste processed, one ton of ash is created.